1. Field of the Invention
The present invention relates to a replica composition for skin comprising a rubber base containing as, a main ingredient, a diorganopolysiloxane and a curing agent. More specifically, it relates to a replica composition suitable for use in the examination or observation of the microstructure of the surface of skin capable of forming a replica in a short time without causing irritation to the skin.
2. Description of the Prior Art
Heretofore, the surface appearance of human skin has been observed or examined by the following methods:
(a) Direct observation by means of a magnifier (or Lupe) or a microscope;
(b) Indirect observation by the so-called "SUMP (i.e., Suzuki's Universal Micro-Printing)" method, wherein a skin replica is obtained by applying a SUMP plate coated with acetone or amyl acetate to human skin and removing the same, after drying; and
(c) Indirect observation by a method wherein a negative replica of human skin is obtained by using a mixture of a rubber base containing, as a main ingredient, diorganopolysiloxane and a curing catalyst and, then, a positive replica is formed from the negative replica (see Japanese Unexamined Patent Publication No. 54-56280).
Method (a) is disadvantageous for the reasons that observation and comparison under uniform conditions are difficult. Therefore, method (b) has been most widely used for the observation of human skin. However, method (b) has problems. For example, stinging, itching, and other skin irritation are caused by the use of the organic solvent; only a flat image (i.e., two-dimensional image) can be obtained by means of a transmission-type microscope as the replica is transparent; and environmental conditions must be carefully maintained for long-term storage of the replica.
The present inventors previously proposed method (c) to solve these problems in the prior art. Method (c) does not cause any irritation to human skin and provides a three-dimensional image suitable for observation having good storage stability. However, this method still has problems in that the operation is troublesome and a relatively long time is required before examination or observation can begin, since a positive replica must be formed from the negative replica.